Coaxial transmission system



Aug. l0, 1937. K. c. BLACK COAXIAL TRANSMISSION SYSTEM Filed April '7, 19.56

5 Sheets-Sheet l /NVENTOR By K. C. BLACK A TTORNEV Aug. 10, 1937.

K. C. BLACK coAXIAL TRANSMISSION `SYSTEM Filed April '7, 1936 3 SheetS-Sheel'I 2` I/VI/ENTO/ A. C. BLACK BVJ1 ATTRNEV ug. 10, 1937. K. c. BLACK l cOAxIAL TRANSMISSION SYSTEM Filed April 7, 1936 5 Sheets-Sheet 3 n @bx mvg/v70@ K C. BLACK A T TURA/5y Patented Aug. 10, 1937 UNITED STATES PATENT OFFICE COAXIAL TRANSMISSION SYSTEM Application April 7, 1936, Serial No. 73,067

7 Claims.

This invention relates to a high frequency transmission system employing coaxial conductor lines, and more particularly to the simultaneous transmission of different frequency ranges over common portions of such lines.

One type of coaxial system comprises two coaxial conductor lines, one for transmitting exclusively in one direction and the other for transmitting similarly in an opposite direction. Oneway attended repeater stations are spaced about fty miles apart along the system while two oneway unattended repeater stations spaced about ten miles apart are positioned on one or both sides of each attended station. Once the coaxial system is placed in operation it is imperative that a failure along its unattended portion be instantaneously detected and reported so that repairs can be effected Without undue interruption of transmission.

v It is an object of the invention to transmit signals in one frequency range over a circuit comprising portions of other circuits used to transmit signals in another frequency range. In the preferred construction to be described herein, the coaxial system is operated under gas pressure in a manner that an alarm indicator at an attended station is operated whenever a predetermined decrease in the gas pressure occurs. A suitable arrangement associated with 1 the alarm indicator enables a quick location of the failure. To facilitate a clearance of the fault, a talking circuit is provided to enable communication between attended and unattended repeater stations. The talking and alarm circuits are provided by utilizing the central conductors of the coaxial conductor lines used to transmit the po-Wer for energizing the repeaters.

The invention will be more fully understood from the following description when read in conynection with the accompanying drawings, in

which Fig. l is a block diagram illustrating two attended repeater stations having interposed therebetween a plurality of unattended repeater sta- .i tions;

Fig. 2 is a schematic diagram delineating one manner of communicatively connecting an attended repeater station with one unattended repeater station;

Fig. 3 is a schematic diagram showing a constant current arrangement for an unattended repeater station that may be used in the circuit of Fig. 2, and

Fig. 4 is a schematic diagram showing a con- .'.xstant voltage arrangement for an unattended repeater station that may be used in the circuit of Fig. 2.

In the following description, the same reference numerals are used whenever the identical elements appear throughout the several figures of the drawings.

In Fig. l attended repeater station III is connected with a remote attended repeater station II by a pair of coaxial conductor lines I2 and I3. Intermediate the attended repeaters lil and 10 II are positioned four unattended repeater stations R1, R2, R3 and R4., each of which includes an eastward one-way amplifier I4 and a westward amplier I5. Attended repeater II) controls unattended repeaters R1 and R2, while at- 15 tended repeater II controls unattended repeaters Rs and R4. The attended repeater stations may be either terminating or intermediate repeater stations. In the latter event, two unattended repeater stations may be located on one or both sides of each thereof. The coaxial conductor lines are operated continuously under gas pressure by a method which isa common practice in the operation of multiconductor telephone cables.

Power from a (iO-cycle source I6 is supplied from attended repeater I through high frequency filters I8 and I9 to unattended repeaters R1 and R2 over a two-wire circuit comprising the central conductors of the pair of coaxial conductor lines I2 and I3. In like manner, power from a (iO-cycle source I'I is supplied from attended repeater II to unattended repeaters R3 and R4. At each unattended repeater, suitable transformers and power units similar to transformer 20 and unit 2I of unattended repeater R1 are provided to take olf power to energize the one-way amplifiers associated therewith. For a more detailed description of the distribution of Gli-cycle power, reference may be had to 0 the patent of M. E. Strieby, No. 2,037,183 issued April 14, 1936.

In the preferred form of the invention show in Fig. l a conventional talking circuit 2t, and alarm indicator 21 and its associated 2Q00--cycle supply 28 are connected in parallel with each other and with the GO-cycle power source It. Therefore, the voice and alarm frequencies are transmitted through high frequency filters I8 and I9 to unattended repeaters R1 and R2 over 50 the central conductors of the coaxial conductor lines I2 and I3, which as previously seen, are utilized to distribute the (S0-cycle power supply between the same repeaters. In a similar manner, the voice and alarm frequencies are transmitted from attended repeater II to unattended repeaters R3 and R4.

At each unattended repeater, a talking circuit and a pair of alarm contactors identical with talking circuit 26 and gas-pressure contactors 29, 29 of repeater R1 are connected across the primary winding of the (iO-cycle power transformer 20. The gas-pressure contactors 29, 29, well known in the operation of multiconductor telephone cables under gas pressure, are attached to the sheath of the coaxial cable so as to effect an alarm in the attended station in a manner that will be subsequently explained. They may be of any suitable type such, for example, as that disclosed in the patent of T. C. Henneberger et al. No. 1,936,194, issued November 21, 1933.

In Fig. 2, the circuit connections of attended repeater I and unattended repeater R1 are shown in detail. Station III comprises a high frequency transmitting apparatus 34 and a high frequency receiving apparatus 35 both of which are preferably in the form of multiplex terminal circuits for respectively impressing on outgoing coaxial conductor line I2 and receiving from incoming coaxial conductor line I3 modulated carrier waves in a large number of channels extending over a frequency range of the order of 1000 kilocycles. Terminal amplifiers 36 and 31 may be energized in any satisfactory manner, not shown. The multiplex transmitting and receiving circuits may be of a suitable type such, for example, as that disclosed in the patent of L. Espenschied et al. No. 1,835,031, issued December 8, 1931.

An alternating source I6 of (S0-cycle power is connected to the primary winding of a transformer 36 that has its secondary winding connected through the filters I8 and I9 to the central conductors of the pair of coaxial conductor lines I2 and I3. By means of the filters I8 and I9, the high frequency signaling currents are precluded from entering the 60-cyc1e power circuit, and the power currents are prevented from traversing the circuits utilized by the signaling currents.

Also, the talking circuit 26 is connected to one side of a D. P. D. 'I'. switch 4I which has its central poles connected to a series circuit 42 comprising parallel networks 43, 43, series network 44, and the secondary windings of inductances 45 and 46. The series circuit 42 shunts the secondary winding of the transformer 38. The networks 43, 43 are designed to provide a relatively high impedance to the GO-cycle power voltage, hence the latter is precluded from endangering the safety of a speaker using the talking circuit 26. The networks 43, 43 are designed also to provide a relatively low impedance to voice and the 200G-cycle frequencies as well as serving as high frequency filters to prevent cross-talk between the coaxial conductor lines I2 and I3 during the transmission of high frequencies. The network 44 is designed to provide a relatively high impedance to voice and 200G-cycle frequencies, and a low impedance to the 60cycle power voltage. Accordingly, when the switch 4I connects the talking circuit 26 to the series circuit 42, voice currents may be transmitted from attended repeater ID through networks 43, 43 and filters I8 and I9 along the central conductors of the coaxial conductor lines I2 and I3 to the unattended repeaters R1 and R2.

Since the alarm `circuit is normally conditioned for operation, a D. P. S. T. switch 41 is closed lto connect the 200G-cycle alarm supply 28 to the primary windings of the inductances 45 and 46.

This impresses continuously a 200G-cycle voltage across the central conductors of the pair of coaxial conductor lines extending between the attended repeater IIJ and unattended repeaters R1 and R2. The transmission is effected in a manner that will be subsequently described. In addition, the switch 4I is normally closed across thermocouple I connected to an ammeter 52. During normal circuit conditions, a variable resistance 53 is set at Zero, and an S. P. S. T. switch 54 is open to connect a fixed resistance 55 across the network 44. The resistance 55 determines the voltage to an alarm indicator 56 whose function and operation will be subsequently explained. The alarm indicator may be of a suitable type such, for example, as either a single rectifier tube and an ordinary direct current relay, or a rectifier tube operating a gas tube that in turn operates a direct current relay.

In unattended repeater R1 of Fig. 2, filters I8 and I9, which are connected similarly to filters I8 and I9 in attended repeater I0, allow the relatively high frequency currents to be impressed on amplifiers I4 and I5, respectively, while at the same time separating the relatively low frequency currents originating in the talking, GO-cycle power, and 200G-cycle alarm circuits to be impressed on their associated apparatus without causing any` interference between the high and low frequencies. After passing the amplifiers I4 and I5, the high frequency currents are impressed on high frequency filters 51 and 58 for transmission to the next unattended repeater. The filters 51 and 58 have circuit connections similar to the filters I8 and I9. The C50-cycle power transmitted from attended repeater I0 over the central conductors of the two coaxial conductor lines I2 and I3 is impressed on the primary winding of transformer 2D having its secondary winding connected to power unit 2I. The latter serves to energize the tubes of the one-way amplifiers I4 and I5. In addition, ISO-cycle power is shunted around amplifiers I4 and I5 by leads 59 and 6I) which connect filters I6 and 51, and I9 and 58, respectively. These connections make the 60- cycle power available at the next unattended repeater for energizing the amplifiers associated therewith.

Also in unattended repeater R1 of Fig. 2, a series circuit 65 comprising networks 43, 43 and 44 is connected in shunt with the primary winding of transformer 26. The networks of this repeater serve the same purpose for which the similarly identified networks are utilized in attended repeater I0. Across the network 44 is a telephone jack 66 that normally connects each contactorof the pair of gas-pressure contactors 29, 29 to the two central conductors employed to transmit the (S0-cycle power between repeater stations. When talking circuit 26 is plugged into the jack 66, the pair of gas-pressure contactors 29, 29 are disconnected and a talking circuit is provided between unattended repeater R1 and attended repeater II) over the two central conductors of the pair of coaxial conductor lines I2 and I3. To complete this talking circuit, it is, of course, necessary to close the switch 4I across the talking circuit 26 located in attended repeater I9- In unattended repeater Rz, which is not shown in detail in Fig. 2, the circuit arrangements required to make available the voice and 200G-cycle alarm currents therein` are identical with those shown in detail in connection with its associated repeater R1. l

- In Figs. l and 2`it will be noticed inunattended repeaters R2 and Re that there are no leads shunting the (iO-cycle power supply around the two one-way'amplilers in a manner similar to that effectedby leads 59 and 60 of unattended repeater R1. The omission of these shunt connections is intended to eliminate the possibility of interconnection between the 60-cycle power sources I6 and I1 located at the remote. repeaters I and I I, respectively. In addition, the absence of the shunt connections also precludes an interconnection between the talking and alarm circuits of the same repeaters.

When the pressure in the coaxial conductor lines is normal, the gas-pressure contactors 29, 29 are open so as to interrupt the alarm circuit which is conditioned for operation as hereinbefore described. When, however, the gas pressure in close proximity to one of the four points covered by the contactors 29, 29 falls below a predetermined value, one of the gas-pressure contactors is closed thereby enabling a 200G-cycle current to flow over the two central conductors of the pair of coaxial conductor lines extending between the attended repeater I0 and either unattended repeater Ri or R2 depending on the location of the fault. The value of this current depends upon the distance of the operated contactor from the attended repeater I0, and, to some extent, upon the line resistance which varies according to weather conditions. The 200G-cycle current iiow develops a voltage across the fixed resistance 55 at attended repeater I0 whereby the alarm indicator 56 is actuated. The indicator 56 warns the operator that a cable failure has occurred somewhere along the unattended portion of the coaxial system, but, however, does not show the location of the failure.

To determine the position of the fault, the switch 54 is closed thereby short-circuiting the fixed resistance 55 to remove the voltage from the alarm indicator 56. Thereafter, resistance 53 is varied to correspondingly increase the 2000- cycle current flowing through the thermocouple I. The value of the current indicated on the associated ammeter 52 enables the determination of the particular gas-pressure contactor that has operated to report the cable failure. To make this possible, a range of current values depending on the range of resistance values of this line circuit is predeterminedly assigned to each gaspressure contactor so that a. Value of current falling within the range indicates immediately the closed gas-pressure contactor.

A constant current arrangement for 60-cycle power distribution for use in unattended repeater R1 is shown in Fig. 3. The circuit connections for this arrangement differ from those of the same repeater in Fig. 2 only with reference to the feature of operation on a constant current basis. For this operation no change in the circuit connections at either attended repeater II] or unattended repeater R2 of Fig. 2 is required. In R1, however, a constant 60-cycle current flows through the primary windings of two transformers 61, 61 used to transmit power to unattended repeater Rz and through the primary winding of transformer 20 connected to a power unit 2I which is utilized to supply 60-cycle power to the one-way amplifiers I4 and I5. It will be noted that the primary winding of transformers 61, 61 and 20 are connected in series. The secondary windings of the transformers 61, 61 are also connected in series so that for a constant current flowing through their associated primary windings, a constant current of a slightly smaller magnitude will be delivered to the sections of the coaxial conductor lines extending between unattended repeaters Ri and R2. Networks 68, 68 connected between the windings of the transformers 61, 61 are designed to present a high impedance to the 60-cycle power, and, in addition, a low impedance to the flow of voice and 2000-cycle currents from unattended repeater R2. The transformers 61, 61 and 20 serve as high impedances to the Voice and 200G-cycle currents. A series circuit 69 connected across the primary windings of transformers 61, 61 and 26 is identical with and performs the same function as the similar circuit 65 in unattended repeater R1 of Fig. 2.

A constant voltage arrangement for (S0-cycle power distribution for use in unattended repeater R1 is shown in Fig. 4. The circuit connections for this arrangement differ from those of the same repeater shown in Figs. 2 and 3 only with respect to the feature of operation on a constant voltage basis. For this operation, no change in the circuit connections of either attended repeater I0 or unattended repeater R2 of Fig. 2 is required. In R1, however, a multiwinding unit is designed to impress a slightly higher voltage on` the coaxial sections extending between Ri and R2 than that impressed on the coaxial sections extending between repeaters IU and Ri. In this way a constant voltage is provided for energizing the one-way amplifiers in unattended repeater R2. The multiwinding unit serves as a high impedance to the voice and 200G-cycle alarm currents. In all other respects the circuits of unattended repeater R1 shown in Fig. 3 and Fig. 4 are alike.

Accordingly, it is seen in Figs. 3 and 4 that Voice and 200G-cycle alarm currents are transmitted over a power distributing circuit shown therein in a manner substantially identical with that described hereinbefore with respect to Figs. 1 and 2.

It will be understood that the invention is capable of modifications without departing from the scope of the invention as defined in the appended claims.

What is claimed is:

1. In a high frequency carrier wave transmission system, a pair of attended stations, a plurality of unattended stations between the attended stations, two coaxial conductor lines connecting the attended and unattended stations, means for transmitting high frequency carrier waves through the unattended stations and between the attended stations in one direction over one coaxial conductor line and in an opposite direction over the other coaxial conductor line, a signaling circuit extending from one of the attended stations to a plurality of unattended stations and comprising the central conductor of one coaxial conductor line as one side and the central conductor of the other coaxial conductor line as the return side, means for impressing low frequency currents on the signaling circuit, filter networks connected in the coaxial conductor lines at each station for preventing interference between the high and low frequency transmission, and a local circuit at each station for deriving the low frequency currents from the signaling circuit to enable signaling communication between the attended and unattended stations.

2. A system according to claim 1 in which the local circuit includes networks for preventing cross-talk between the coaxial conductor lines during transmission.

3. In a high frequency carrier wave transmis sion system, a pair of attended repeater stations, a plurality of unattended repeater stations intermediate the attended stations, two coaxial conductor lines connecting the attended and unattended repeater stations, means for transmitting high frequency carrier waves between the attended stations in one direction over one coaxial conductor line and in an opposite direction over the other coaxial conductor line, a low frequency power supply at each attended station, a circuit comprising the central conductors of the two coaxial conductor lines for transmitting the power supply between the attended station and at least one unattended station, means for impressing other low frequency currents on the power transmitting circuit, fllter networks connected in the coaxial conductor lines at each station for preventing interference between the high and low frequency transmission, means at the unattended stations for deriving power from the power circuit and rendering same available thereat, and a local circuit at each station for deriving the other low frequency currents from the power circuit to enable signaling communication between the attended and unattended repeater stations.

4, In a high frequency carrier wave systemfa pair of attended stations, a plurality of unattended stations between the attended stations, a. pair of coaxial conductor lines connecting the stations, means for transmitting high frequency carrier Waves between the stations in one direction over one coaxial conductor line and in an opposite direction over the other coaxial conductor line, a signaling circuit extending from one of the attended stations to a plurality of unattended stations and comprising the central conductor of one coaxial conductor line as one side and the central conductor of the other coaxial conductor line as the return side, the co axial conductor lines being operated under a predetermined gas'pressure, means at the attended stations for continuously impressing a low frequency signaling current on the signaling circuit, a circuit at each station for deriving the signaling current from the signaling circuit, means attached to each coaxial conductor line passing through the unattended stations and operatively connected in the last-mentioned circuit for normally interrupting the signaling current under the predetermined gas pressure and closing the signaling circuit when the gas pressure falls below the predetermined amount due to a failure of the coaxial conductor lines, and an alarm indicator actuated in the attended station in response to the closed signaling circuit to report a failure along an unattended section of the coaxial conductor line.

5. A system according to claim 4 in which means is provided to locate the failure after the alarm indicator has reported the existence thereof.

6. A system according to claim 3 in which the local circuit includes networks for deriving low frequency currents from the power circuit at one unattended repeater arranged for a constant current operation.

7. A system according to claim 3 in which the local circuit includes networks for deriving low frequency currents from the power circuit at one unattended repeater arranged for a constant voltage operation.

KNOX C. BLACK. 

